1. Field of the Invention
The present invention relates to an electron tube for communication such as a traveling-wave tube or klystron that is used in communication devices.
2. Description of the Related Art
An electron tube for communication such as a traveling-wave tube or klystron is a RF (Radio-Frequency) device for amplifying or oscillating microwaves by means of the interaction between an electron beam that is emitted from an electron gun and a RF circuit. As shown in FIG. 1, an electron tube for communication is a construction that includes, for example: electron gun 3 for emitting electron beam 2, RF circuit 4 for bringing about interaction between a RF signal (microwave) and electron beam 2 that is emitted from electron gun 3, collector 5 for capturing electron beam 2 that is passed from RF circuit 4, and anode electrode 6 for guiding electron beam 2 that has been emitted from electron gun 3 into RF circuit 4. As an example of an electron tube for communication, FIG. 1 shows the construction of a traveling-wave tube.
Electron beam 2 that has been emitted from electron gun 3 is guided into RF circuit 4 by anode electrode 6 and travels inside RF circuit 4 while interacting with a RF signal that has been received as input by RF circuit 4. The electron beam that is supplied as output from RF circuit 4 is received by collector 5, and captured by a collector electrode that is provided in collector 5. The RF signal that is amplified by the interaction with electron beam 2 is then supplied as output from RF circuit 4.
As shown in FIG. 2, inside RF circuit 4 of the traveling-wave tube, a RF signal is received as input from input coaxial unit 7, and following amplification, the RF signal is supplied as output by way of output coaxial line 8 to output waveguide 9 that is provided on the side wall of traveling-wave tube 1.
Output waveguide 9 is directly coupled to the collection port of the RF signal, and output coaxial line 8 is secured to a prescribed position of the sealed end side of output waveguide 9 by means of ceramic window 10 for vacuum sealing the interior of RF circuit 4.
Flange 11 is provided for connection with other waveguides at the end of output waveguide 9 that is opposite the sealed end, and, for example, isolator 20 that is constituted by a waveguide, low-pass filter 30, and high-pass filter 40 are attached as shown in FIG. 3. The RF signal that has been irradiated into output waveguide 9 from traveling-wave tube 1, having passed through these attachments to eliminate noise that is outside the bandwidth, i.e., frequency components that are not required by the system, is radiated from a transmission antenna (not shown in the figure). The configuration that is shown in FIG. 3 is the construction disclosed in Patent Document 1 (Japanese Patent Laid-Open Publication No. 58543/1995).
To allow installation on, for example, artificial satellites or aircraft, communication devices that are provided with an electron tube for communication such as a traveling-wave tube or klystron must be compact and lightweight.
In Patent Document 1, a construction is proposed for reducing the size and weight of the overall antenna device that includes a traveling-wave tube in which a primary radiator that is positioned at the focal point of a reflecting mirror is supported and secured by, for example, the above-described isolator that is composed of a waveguide, low-pass filter, and high-pass filter.
However, reducing the size and weight has been problematic because the size of the traveling-wave tube itself is substantially determined by specifications of the communication device that include the transmission frequency, transmission power, and power consumption.